The correct answer is option 4: Insulin is a protein hormone which is produced in the human body.

Insulin is a hormone that plays a crucial role in regulating blood sugar levels. It is produced in the pancreas by specialized cells called beta cells. These beta cells synthesize insulin as a polypeptide chain, which is then modified and folded into its active form.

Option 1 is incorrect because insulin is indeed produced in the human body. Its production is necessary for maintaining healthy blood sugar levels.

Option 2 is incorrect because insulin is not a steroid hormone. Steroid hormones, such as cortisol or testosterone, are derived from cholesterol and have different functions in the body.

Option 3 is incorrect because insulin is not cholesterol-driven. While cholesterol is a precursor for the synthesis of certain hormones, insulin is not one of them.

In conclusion, option 4 accurately states that insulin is a protein hormone produced in the human body.